The present invention relates generally to disc storage subsystems, and more particularly, but not by limitation, to a disc storage subsystem having redundant controllers for improved reliability.
A disc storage subsystem generally includes a housing in which a plurality of disc drives are stored in removable carriers. Each disc drive includes a connector that interfaces with a corresponding connector of a midplane card to provide data communication therebetween. A controller, stored in a rear portion of the housing, includes an electrical connection with the midplane card for data communication with the disc drives. External processing electronics, such as a host computer, can access the data stored in the disc drives through the controller.
Each disc drive of the subsystem includes a data interface, through which the data stored therein is accessed. One such data interface is the Advanced Technology Architecture (ATA) data interface. This data interface can be serial (SATA) or parallel (PATA) data interface. The ATA data interface only provides single channel communication with the disc drive. Thus, disc storage subsystems using such ATA disc drives include only one controller, through which the data can be accessed by a host computer.
It is important that disc storage subsystems provide reliable data storage. To that end RAID (Redundant Array of Independent Disks) architectures are employed. In such architectures, the subsystem includes one or more additional disc drives storing redundant data. Thus, in the event of a disc drive failure the data is safely maintained by the other disc drives. Accordingly, such an arrangement can prevent the catastrophic loss of data.
Unfortunately, such a redundant arrangement of disc drives does not ensure that the data stored in the disc drives remains continuously accessible. Obviously, if a disc drive fails, the data stored in that particular disc drive becomes inaccessible, but is still accessible from the redundant disc drives. However, data stored in the disc drives becomes inaccessible in the event of a controller failure in a subsystem that utilizes ATA disc drives. In that case, the disc storage subsystem must be shut down and the controller replaced, before the data becomes accessible once again. This is commonly known as a single point of failure for the disc storage subsystem.
Embodiments of the present invention provide a solution to this and other problems, and offer advantages over the prior art.
The present invention is directed to a disc storage subsystem that allows continued access to data stored in its Advanced Technology Architecture (ATA) disc drives in the event of a controller failure. The disc storage subsystem includes a housing, at least one disc drive assembly, first and second controllers, and an intermediate electronic component. The disc drive assembly is received in a front portion of the housing and includes a disc drive contained in a carrier. The disc drive includes an ATA data interface including a connector. The first and second controllers each include a data port corresponding to the disc drive. The intermediate electronic component includes multiplexing electronics having first and second data communication paths. The first data communication path provides electronic communication between the data port of the first controller and the data interface of the disc drive. The second data communication path provides electronic communication between the data port of the second controller and the data interface of the disc drive. The multiplexing electronics selectively opens and closes the first and second data communication paths in response to at least one control signal. In this manner, redundant controllers are established in the disc storage subsystem such that data stored in one of the disc drives remains accessible to a host computer through either the first or the second controllers in the event that one of them fails.
Other features and benefits that characterize embodiments of the present invention will be apparent upon reading the following detailed description and review of the associated drawings.